Clamping attachment for industrial trucks



2 Sheets-Sheet 1 W. R. MENZEL ETAL w 3 ww eooeooooooo 088@@@ t. w 9 :A 3 -p w m d \mm mm mm mm NM NM qm vm Sept. 5, 1961 CLAMPING ATTACHMENT FOR INDUSTRIAL TRUCKS Filed. Feb. 15, 1959 m mmmommm INVENTORS. WERNER R. MENZEL BY MATTHIAS WILLMS ATTY.

P 5, 1961 w. R. MENZEL EI'AL 2,998,892

CLAMPING ATTACHMENT FOR INDUSTRIAL TRUCKS Filed Feb. 13, 1959 2 Sheets-Sheet 2 lml . INVENTORS. WERNER R. MENZEL MATTHIAS WILLMS VKMA'WJIV ATTY.

'1 Patented Sept.'5', 1961.

v 2,998,892 CLAMPING ATTACHMENT FOR INDUSTRIAL TRUCKS Werner R. Menzel, Muelheim, and Matthias Willms, Eschweiler, Germany, assignors to Ruhr Intrans Hubstapler G.m.b.H., a German company.

Filed Feb. 13, 1959, Ser. No. 793,066 4-Claims." (Cl. 214-655) This application relates to attachments for industrial lift trucks and the like, and more particularly to clamping attachments which are used with such machines for the gripping, moving, and stacking of bulk goods such as billets, logs, bars and the like.

\ While industrial lift trucks are most frequently equipped with fork tines projecting from the front for engaging pallets for, lifting, transporting, and elevating loads supported on the pallets, it is well known to use clamp devices on such machines. Normally, such devices engage the sides of a load with sutficient pressure to enable the machine to pick up the load without the use of forks and without a pallet. One common application, for example, of clamp attachments is in the handling of bricks, concrete blocks and the like where it is common practice to tier several layers of bricks or blocks and then pick up the entire stack by clamping the bottom layer. A clamp attachment of this type is disclosed in the co-. pending US. patent application Serial No. 495,968, filed March 22, 1955, now Patent No. 2,896,994, in the name of Herbert Fischer (common assignee). I

The type of clamping attachment above generally identified has been found inappropriate for handling bulk materials such as billets, wood in log or split-log form, tubular bar, and the like. Wood in log or split-log form, for instance, serves as basic material for many industries and is normally bundled and stored in large quantities. In many cases the bundling is accomplished by hand, with the involvement of much labor.

It is known that large consumers of wood in such forms operate with expensive large-scale installations in which the logs are thrown by belts on large piles for subsequent removal with overhead grippers. This method is not satisfactory with certain types of wood, because the wood is not adequately ventilated. Round wooden tongs are often times used as crane apparatus in ship stowage operations. Such tongs normally engage a quantity of wood by penetrating into the pile under their own weight and then a closing force is applied to the tongs.. Suchtongs have also previously been used as attachments on fork lift trucks, mobile cranes, excavators, and the like.

' The use of such a device for this purpose has been found to be rather unsatisfactory because the holding force which is applied to the logs tends to differ with each gripping operation. A very heavy construction of the tong device is usually required in order for it to penetrate adequately into the pile. Frequently such tongs loose a part of the material gripped if the gripper cannot be completely closed, either because the logs are disposed at. an undesirable angle relative to the tongs or because the tongs may grip too bulky a load. Frequently, logs of predetermined length shift longitudinally both in the closing and also in the opening of the gripper tongs, which requires considerable additional manual labor in order to restore the logs to correct position.

The present invention overcomes the various drawbacks of prior devices for handling materials of the type contemplated.

In carrying out our invention in one preferred form thereof, we provide an hydraulically operated gripper which grips material, such as split wood, round wood, or other material of similar form, such as bars and pipes,

from above and on the face or cut surfaces of the material;

in which process variations in length of the material is compensated for by mechanically or hydraulically movable pistons mounted upon one or both of the clamping jaws to move in a direction axial of the material being handled With round wood, for example, it is advantageous to em-' ploy the holding pistons at the edges only of the clamping jaws, whereby the lowermost row of material supports the entire load.

With such a device, burrowing into a pile of material to engage a load becomes unnecessary. The gripping capacity of the device can, for this reason, be made as large or as small as desired. The shape of'the device is preferably designed in such away that the material held yields an approximately rectangular block, which can be located, for instance, in standard cars of the same or multiple capacity without waste of space. If desired, the gripper surface or frame of the gripping surface can receive a trapezoidal form in order to avoid subsequent dropping and angular displacement of individual logs'or the like following deposit of a load. With piles of split pistonswhich are mounted on the inside of the gripper surfaces of the clamping device, which will be described in detail herein-after, may be either mechanicallyoperated by spring on lever action, or hydraulically operated. A

single embodiment is disclosed inthis application which illustrates hydraulically actuated compensating pistons which are connected together by a pressure equalizing system.

In the drawings:

;FIGURE 1 shows a side elevation of the clamping mechanism associated with the upright structure of an industrial lift truck;

FIGURE 2 is a sectional view taken on line 2--2 of FIGURE 1; and I FIGURE 3 is an enlarged sectional view taken on line 3-3 of FIGURE 2. 7

Referring now in detail to the drawings, the clamping device is illustrated generally at numeral 10 in FIGURE 1. Itis attached by a bracket means 12 to a vertically movable lifting carriage 14 of a known upright m'ast construction 16 of an industrial lift truck. Device '10 comprises a fixed clamp portion 18 and a movable clamp portion 20.

Clamp portion 18 comprises a pair of forwardly extending and laterally spaced channel members 22 secured together between the upper legs thereof by a plate 24 and between the lower legs thereof at the'rearw'ard portion of the channel members by a plate 25. The plate 26 extends a substantial distance transversely outwardly of opposite sides of the channel members and has so cured, as by welding, to the bottom surface thereofa generally rectangular, downwardly depending fixed clamp arm 30.

The movable portion 20 of the clamp comprises a pa r of forwardly extending and transversely spaced rails 32 which are mounted inwardly of channel members 22, being connected to the channel members by means of pairs of rollers, one of which pairs is shown at numeral 34, for telescopical movement in either direction longitudinally of fixed clamp portion 18. Plates 36 are seicured to the lower edges of respective ones of rails 32 at 3 the forward ends thereof, the undersides of plates 36 being secured to the upper surface of a clamp arm supporting plate 38. Depending downwardly from the plate 38 is a generally rectangular movable clamp arm 40 which preferahly corresponds in size and shape to fixed clamp arm 30.

Side members 42 and bottom member 44 of the clamp arm 40 are preferably interconnected and braced by a plurality of horizontally, vertically and diagonally disposed members forming a latticeworl: 46. A plate member 48 extends transversely of the forward side of clamp arm 40, being secured along its margin to members 42 and 44. Fixed clamp arm 30 is preferably constructed in a manner similar to clamp arm 40.

A plate member 50 extends between rail members 32 adjacent the forward ends thereof and has connected thereto a piston rod 52 of an hydraulic cylinder and piston assembly, not shown, which is secured at its base or cylinder end to a member extending between channel members 22 rearwardly thereof. The cylinder assembly is operated by hydraulic 'pressurizing means located on the truck for extending and retracting the movable portion 20 of the clamp arm assembly, two positions of the movable portion being shown in FIGURE 1.

Referring to FIGURE 3 it will be seen that each of the side and bottom portions 42 and 44 include spaced plates 56 and 58 between which are mounted in spaced relation a plurality of hydraulic holding devices 54. Each holding device 54 comprises a cylinder 60 in which is mounted for reciprocation a piston element 62 having a rearwardly extending piston rod 64 associated therewith and in facing relation to fixed arm 30. Each of the cylinders 60 is sealed at its one end by means of a cover plate 66 and communicates at its other end with an bydraulic conduit 68 through a passageway 70. Conduit 68 interconnects the one ends of all of the cylinders 60 of holding devices 54 and is adapted to receive pressure fluid from a source, not shown, located on the vehicle.

In FIGURE 1, the fixed clamp arm 30 includes holding devices 54 which correspond to the holding devices located on the movable clamp arm 40. Although it is preferred that the holding devices be utilized with both clamp arms, it is not essential. However, it will be readily seen that if roughly cut lengths of such material result in substantial variations in the length thereof, use of the holding devices on both the fixed and movable arms will enable the attachment to be effectively used with material having substantially greater variations in length than if the holding devices are utilized with only one of the arms.

In operation, the truck approaches a stack of logs, bars, or the like, with the clamping device 10 elevated on upright 16 above the topmost row of material. The clamping device in side view is in the form ofan inverted generally U-shaped device. With the clamping device so located and the movable clamp arm 20 extended forwardly of fixed arm 18 the distance necessary to span the length of material to be handled, the clamping device is lowered so as to be disposed astride such material. The cylinder assembly for actuating the movable clamp arm is then energized to retract said clamp arm so as to actuate the ends of at least some of piston rods 64 into abutment with the end or cut surfaces of the longer logs or other units of the load. This may, for example, require a movement of the clamping arm 20 from the solid line position illustrated in FIGURE 1 to the dotted line position thereof. The cutor end-surfaces of the units of the load which are located adjacent the fixed arm portion 30 are also brought into abutment with the clamp arm 30 or with holding devices -3 thereof.

Following a proper positioning between the clamp arms of a unit load, pressure fluid is introduced into conduit 68 which is applied equally to each of the pistons 62 of the holding devices. Depending of course, .upon the variation in length of the various units of the load willdetermine the amount of extension required of the various piston rods 64. The shorter the relative length of some units of the load, the greater is the extension required of the corresponding piston rods. In any case, the various piston rods extend as required, within limits, to engage with equal holding forces the end or cut surfaces of those units of the load which are located between the boundary portions of clamp arms 30 and 40. Thus, the unit load is positively held in position between the clamp arms with the lower row and opposite sides of the unit load supporting the remainder of the load during transport thereof by the truck.

It will now be understood that in the use of my invention discrete loads may be engaged by engaging boundary units of the load lengthwise thereof despite differences in the lengths of the various units, and that such loads may be then transported and disengaged at selected locations.

Although only one embodiment of the invention has been specifically disclosed, it will be apparent to persons skilled in the art that modifications in the construc tion and arrangement of the parts may be made without departing from the scope of the invention as defined in the claims.

We claim:

1. A clamping attachment for use with industrial trucks having an upright mast mounted at one end thereof comprising a fixed clamp portion mounted for elevating movement in the mast, a movable clamp portion telescopical inwardly and outwardly of the fixed clamp portion for engaging a load therebetween, each of said clamp portions including a downwardly depending clamp arm, at least one of which arms includes peripheral edge portions which define the lateral and lower boundary areas of the arm, a plurality of hydraulic holding de vices mounted in said edge portions including piston elements extending therefrom in facing relation to the other clamp arm, a cylinder element associated with each piston element, and pressure fluid conduit means interconnecting the cylinder elements of said holding devices for introducing equal pressure fluid in said cylinder elements, said piston elements being variably extensible outwardly of the respective cylinder elements for clamping load units of varying length between the clamp arms.

2. A clamping device for use with industrial trucks having an upright mast mounted at one end thereof comprising an elevatable inverted generally U-shaped clamp which extends from the mast longitudinally of the truck for engaging and transporting a plurality of load units such as cut logs, split Wood, bars, pipes and the like, of varying length, including a pair of downwardly depending longitudinally spaced load engaging members forming complementary four-sided clamp arms of the clamping device, one of said clamp arms being fixed in a longitudinal direction of the truck and the other clamp arm being movable in a longitudinal direction of the truck, extensible means connecting the upper ends of said clamp arms for actuating said other clamp arm longitudinally of the truck and toward and away from said one clamp arm, and a plurality of hydraulic holding devices mounted upon and projecting horizontally inwardly from the bottom side of one of the clamp arms and from the generally vertically extending opposite side portions of said latter clamp arm, said holding devices being energized by pressure fluid to project inwardly to a greater or lesser degree toward the other clamp arm, whereby to abut and hold between the clamp arms in a direction longitudinal of the truck a plurality of units of varying length.

3. A clamping device as claimed in claim 2 wherein each holding device comprises a cylinder-piston assembly the piston rod of which projects horizontally as aforesaid, and hydraulic conduit means interconnecting the cylinders of said holding devices for applying equal pressure to the piston elements thereof.

4. A clamping device as claimed in claim 2 wherein of a load which extends longitudinally between correa plurality of said holding devices are also located on the p nding devi e8- other clamping arm in opposed relation to the first men- References Cited in the file of this patent tioned holding devices, whereby the inverted generally UNITED STATES PATENTS U-shaped clamping device may engage and clamp be- 5 2,247,168 Fontaine June 24, 1941 tween the holding devices of the pair of clamp arms 2,735,713 Blakeley Feb. 21, 1956 thereof a plurality of discrete units of varying length 90 Vandemark Sept. 18, 1956 

